Here you have a great case study, about an organization that tried to do a volunteer model, and it didn't work. Then they pivoted to a commercial model, but fundamentally they still believe in a free tier. But they have to cripple that free tier pretty thoroughly, and even still people abuse it.
I have a product I'm working on, that some people are apparently willing to spend lots of money on. Ideally I would have some kind of low tier, so that people without lots of money would be able to use it too. But I can't figure out a way to segment the product so that everybody pays what they can afford without bad apples abusing the low tier and ruining it for everybody. The result is that I may end up only selling it to customers with deep pockets, even though the product is much more broadly applicable.